Direct numerical simulation and large eddy simulation of turbulent pipe flow

Direct Numerical Simulations and Large Eddy Simulations are performed for a fully developed turbulent pipe flow in non-rotating and rotating cases. The aim of this study is to investigate the effects of the Reynolds number and of the rotation number on the turbulent flow characteristics. The mean velocity profiles and many turbulence statistics are compared to numerical and experimental data available in the literature, and reasonably good agreement is obtained. In particular, the results show that the axial velocity profile gradually approaches a laminar shape when increasing the rotation rate, due to the stability effect caused by the centrifugal force. Consequently, the friction factor decreases. The Reynolds number dependence of the mean velocity profile decreases when the rotation rate increases. The rotation of the wall has large effects on the root mean square (rms), these effects being more pronounced for the streamwise rms velocity. Visualizations of the instantaneous velocity and vorticity fields exhibit turbulence structures with strong vorticity developing up to the pipe centre. These vortical structures are inclined and better organized with increasing N.